/**
 * Copyright (c) 2005-2011 springside.org.cn
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * 
 * $Id: DigestUtils.java 799 2009-12-31 15:34:10Z calvinxiu $
 */
package com.se7en.core.utils.security;

import java.io.IOException;
import java.io.InputStream;
import java.security.GeneralSecurityException;
import java.security.MessageDigest;

import com.se7en.core.utils.EncodeUtils;
import com.se7en.core.utils.ExceptionUtils;

/**
 * 支持SHA-1/MD5消息摘要的工具类.
 * 
 * 支持Hex与Base64两种编码方式.
 * 
 * @author calvin
 */
public abstract class DigestUtils {

    private static final String SHA1 = "SHA-1";

    private static final String MD5 = "MD5";

    // -- String Hash function --//
    /**
     * 对输入字符串进行sha1散列, 返回Hex编码的结果.
     */
    public static String sha1Hex(String input) {
        byte[] digestResult = digest(input, SHA1);
        return EncodeUtils.encodeHex(digestResult);
    }

    /**
     * 对输入字符串进行sha1散列, 返回Base64编码的结果.
     */
    public static String sha1Base64(String input) {
        byte[] digestResult = digest(input, SHA1);
        return EncodeUtils.encodeBase64(digestResult);
    }

    /**
     * 对输入字符串进行sha1散列, 返回Base64编码的URL安全的结果.
     */
    public static String sha1Base64UrlSafe(String input) {
        byte[] digestResult = digest(input, SHA1);
        return EncodeUtils.encodeUrlSafeBase64(digestResult);
    }

    /**
     * 对字符串进行散列, 支持md5与sha1算法.
     */
    private static byte[] digest(String input, String algorithm) {
        try {
            MessageDigest messageDigest = MessageDigest.getInstance(algorithm);
            return messageDigest.digest(input.getBytes());
        } catch (GeneralSecurityException e) {
            throw ExceptionUtils.unchecked(e);
        }
    }

    // -- File Hash function --//
    /**
     * 对文件进行md5散列, 返回Hex编码结果.
     */
    public static String md5Hex(InputStream input) throws IOException {
        return digest(input, MD5);
    }

    /**
     * 对文件进行sha1散列, 返回Hex编码结果.
     */
    public static String sha1Hex(InputStream input) throws IOException {
        return digest(input, SHA1);
    }

    private static String digest(InputStream input, String algorithm) throws IOException {
        try {
            MessageDigest messageDigest = MessageDigest.getInstance(algorithm);
            int bufferLength = 1024;
            byte[] buffer = new byte[bufferLength];
            int read = input.read(buffer, 0, bufferLength);

            while (read > -1) {
                messageDigest.update(buffer, 0, read);
                read = input.read(buffer, 0, bufferLength);
            }

            return EncodeUtils.encodeHex(messageDigest.digest());

        } catch (GeneralSecurityException e) {
            throw ExceptionUtils.unchecked(e);
        }
    }

}
